Cod

The white, mild flavored flesh of cod is available throughout the year and is a wonderful substitute for meat protein with its versatility making it easily adaptable to all methods of cooking.

Cod belong to the same family (Gadidae) along with both haddock and pollock. It's not surprising that the words "cod" and "cold" are so similar since cod need the cold, deep, Arctic waters to grow, reproduce and survive.

Health Benefits

Besides being an excellent low-calorie source of protein (a four-ounce serving of cod contains over 21 grams), cod contains a variety of very important nutrients and has also been shown to be useful in a number of different health conditions.

Cardiovascular Benefits

Fish, particularly cold water fish like cod, have been shown to be very beneficial for people with atherosclerosis and diabetic heart disease. Studies show that people who eat fish regularly have a much lower risk of heart disease and heart attack than people who don't consume fish. Cod, specifically, promotes cardiovascular health because it is a good source of blood-thinning omega-3 fatty acids as well as an excellent source of vitamin B12 and a good source of vitamin B6, both of which are needed to keep homocysteine levels low. This is important because homocysteine is a dangerous molecule that is directly damaging to blood vessel walls, and high homocysteine levels are associated with a greatly increased risk of heart attack and stroke(homocysteine is also associated with osteoporosis, and a recent study found that osteoporosis occurred more frequently among women whose vitamin B12 status was deficient or marginal compared with those who had normal B12 status.) Cod is also a very good source of niacin, another B vitamin that is often used to lower high cholesterol levels, something else that can lead to heart disease.

Increases Heart Rate Variability—A Measure of Heart Muscle Function

One of the ways in which consuming fish rich in omega-3 fats, such as salmon, promotes cardiovascular health is by increasing heart rate variability (HRV), a measure of cardiac function, in as little as three weeks, according to a study published in the April 2005 issue of Chest.

Researchers from Atlanta, GA, Boston, MA, and Cuernavaca, Mexico, took the HRV of 58 elderly patients every other day for two months to establish an HRV baseline for each participant. For the next 11 weeks, half of the study participants took a daily 2 gram supplement of fish oil and the other half took a daily 2 gram supplement of soy oil.

Patients in both groups experienced a significant increase in HRV, with those who took fish oil achieving a greater increase in a shorter time period. Patients who received fish oil experienced increased HRV within the first 2.7 weeks, whereas it took 8.1 weeks for a significant increase in HRV to be seen in the group taking soy oil.

On the other hand, while none of the study participants experienced significant negative side effects, 41% of participants in the fish oil group reported belching, compared to 16% in the soy oil group.

"Our findings contradict the current belief in the medical community that increasing the intake of omega-3 fatty acids produces only long-term cardiac benefits," said the study's lead author, Fernando Holguin, MD, Emory University School of Medicine, Atlanta, GA. "In fact, our study group showed improvements in heart function in as little as two weeks."

"Studies like this demonstrate that there are additional approaches we can take to protect ourselves from heart attacks," said Paul A. Kvale, MD, FCCP, President of the American College of Chest Physicians. "It's exciting to see the potential for omega-3 fatty acids in improving heart function when it complements a healthy lifestyle of exercising, maintaining a healthy weight, and getting eight hours of sleep."

We'd add eating healthful foods to this proactive list. Rather than pop a daily pill, we'd rather enjoy a daily "dose" of delicious cod, soyfoods, or tuna. For recipes certain to not only increase your heart rate variability but also your delight in eating, click Recipes.

Protection against Fatal Heart Arrhythmia

A healthy way of eating that includes at least 10 ounces of omega-3-rich fish each week improves the electrical properties of heart cells, protecting against fatal abnormal heart rhythms, suggests a study from Greece.

"Long-term consumption of fish is associated with lower QT interval in free-eating people without any evidence of cardiovascular disease. Thus, fish intake seems to provide anti-arrhythmic protection at a population level," wrote the authors in the American Journal of Clinical Nutrition. (Chrysohoou C, et al.)

The QT interval is a measure of the heart's electrical cycle, from the beginning of ventricular depolarization, the Q wave, to the end of the T wave, at which point cardiac repolarization is complete.

A lower QT score indicates a lower resting heart rate. As a higher resting heart rate has been linked to an increased risk of sudden death, the result of approximately 50% of heart attacks, lowering the resting heart rate provides significant health benefit.

Researchers at the University of Athens enrolled 3,042 people (1,514 men, aged 18-87, and 1,528 women, aged 18-89), who used a validated food frequency questionnaire to record their food intake of 156 different foods. Along with alcohol consumption and physical activity were also recorded, and electrocardiography was used to measure several indexes of study participants' heart rate.

After the raw data scan, those who ate more than 10 ounces (300 grams) of fish per week were found to have QT scores 13.6% lower than people who did not eat fish.

After adjusting the results for potentially confounding factors such as age, sex, physical activity status, BMI, smoking habits and intake of nuts, the reduction in QT scores in those eating 10 or more ounces of fish each week rose to 29.2%, compared to those who did not eat fish.

In an earlier study, Harvard researchers reported that among those consuming the most fish, heart rate was 2.3 beats per minute lower and likelihood of prolonged QT was 46% lower. Similar results were found in study participants taking 1 gram of omega-3s daily. The mechanism behind these benefits is thought to be omega-3 fats' effects on the flow of sodium and calcium in the ion channels, which are involved with electrical signaling in cells.

Practical Tip: A typical serving of fish is 4 ounces, so just 3 servings of omega-3-rich fish, such as cod, each week would provide 2 ounces more than the 10 ounces this research indicates confers significant protection against sudden death from a heart attack. For great, quick and easy recipe ideas, take a look at our Recipe Assistant.

Eating fish, such as cod, as little as 1 to 3 times per month may protect against ischemic stroke (a stroke caused by lack of blood supply to the brain, for example, as a result of a blood clot), suggests a meta-analysis of 8 studies published in the July 2004 issue of Stroke.

Data on nine independent groups participating in eight different studies found that, compared to those who never consumed fish or ate fish less than once per month, risk of ischemic stroke dropped:

9% in those eating fish 1 to 3 times per month

13% in those eating fish once per week

18% in those eating fish 2 to 4 times per week

31% in those eating fish 5 or more times each week

Just Two Servings of Omega-3-rich Fish a Week Can Lower Triglycerides

Triglycerides are a form in which fat is carried in your bloodstream. In normal amounts, triglycerides are important for good health because they serve as a major source of energy. High levels of triglycerides, however, are associated with high total cholesterol, high LDL (bad) cholesterol and low HDL (good) cholesterol), and therefore, with an increased risk of cardiovascular disease.

In addition, high triglycerides are often found along with a group of other disease risk factors that has been labeled metabolic syndrome, a condition known to increase risk of not only heart disease, but diabetes and stroke. (Metabolic syndrome is the combined presence of high triglycerides, increased blood pressure, high blood sugar, excess weight, and low HDL (good) cholesterol.)

Triglyceride Levels

Less than 150 mg/dL

Normal

150-199 mg/dL

Borderline-high

200-499 mg/dL

High

500 mg/dL

Very High

*Note: Triglycerides are most accurately measured after an 8-12 hour fast.

In this 6-month study involving 142 overweight men and women with high triglycerides, subjects were divided into 5 groups, one of which served as a control group, 2 of which ate 2 servings of fish high in omega-3s while also replacing their normal household fats with fat high in sunflower (Group 1) or canola oil made from rapeseed (Group 2), and 2 of which ate 2 weekly servings of white fish while also replacing their normal household fats with ones high in sunflower (Group 3) or canola oil made from rapeseed (Group 4).

Canola oil also provides some omega-3 fats, with an omega-6:omega-3 ratio of 2:1, while sunflower oil contains omega-6, but no omega-3 fats.

At the end of the study, triglyceride levels had dropped 6.6% in the omega-3-rich fish groups combined. Triglycerides dropped most—10.4%—in those consuming omega-3-rich fish and canola oil. In those eating omega-3-rich fish and sunflower oil, triglycerides dropped 2.8%.

Bottomline: A healthy way of eating that incorporates at least 2 weekly servings of fish and other food sources of omega-3 fats, such as flaxseed or canola oil, may significantly lower triglyceride levels. Replacing normal household fats with flaxseed oil, in which the ratio of omega-6:omega:3 fats is 1:4, might result in an even larger drop in triglyceride levels.

While as little as a weekly serving of fish lowers risk of ischemic stroke, enjoying a daily serving omega-3-rich fish, such as cod, provides significantly greater reduction in the risk of coronary heart disease than eating fish even as frequently as a couple of times a week, show the findings of a study published in the January 17, 2006 issue of Circulation, the journal of the American Heart Association.

Researchers in Japan followed 41,578 men and women aged 40 to 59, none of whom had cardiovascular disease or cancer when the study began, from 1990-1992 to 2001. Food frequency questionnaires completed at the beginning of the study and in 1995, provided information on weekly fish intake, which was analyzed for omega-3 content.

When individuals whose fish consumption was in the top one-fifth of participants at 8 times per week were compared to those whose intake was in the lowest fifth at once per week, they were found to have a 37% lower risk of developing coronary heart disease and a 56% percent lower risk of heart attack.

When the effect of omega-3 fatty acid intake on cardiovascular risk was analyzed, coronary heart disease risk was lowered by 42% among those whose intake was the highest at 2.1 grams per day or more compared to those whose intake was the lowest at 300 milligrams per day. Those whose intake of omega 3s was in the top fifth received a 65% reduction in the risk of heart attack compared to those whose omega 3 intake was lowest.

The authors theorize that daily fish consumption is highly protective largely due to the resulting daily supply of omega-3 fatty acids, which not only reduce platelet aggregation, but also decrease the production of pro-inflammatory compounds called leukotrienes. Lowering leukotrienes reduces damage to the endothelium (the lining of the blood vessels), a key factor in the development of atherosclerosis.
"Our results suggest that a high fish intake may add a further beneficial effect for the prevention of coronary heart disease among middle-aged persons," note the study's authors.

Choose Broiled or Baked, but Not Fried Cod

Eating cod that's broiled or baked, but not fried, may reduce risk of atrial fibrillation, the most common type of heart arrhythmia, especially in the elderly, according to a Harvard study published in the July 2004 issue of Circulation. In the 12-year study of 4,815 people 65 years of age or older, eating canned tuna or other broiled or baked fish 1 to 4 times a week correlated with increased blood levels of omega-3 fatty acids and a 28% lower risk of atrial fibrillation. Eating broiled or baked fish 5 times a week lowered risk even more—a drop in atrial fibrillation risk of 31%.

Eating fried fish, however, provided no similar protection. Not only is fried fish typically made from lean fish like cod and Pollack that provide fewer omega-3 fatty acids, but in addition, frying results in the production of damaged, free-radical-laden fats in the fish as well as the frying oil.

In further research to determine if the omega-3 fats found in fish oil were responsible for fish's beneficial effects on the heart's electrical circuitry, Dariush Mozaffarian and colleagues from Harvard Medical School analyzed data on fish intake and electrocardiogram results from 5096 adults, aged 65 or older, who were enrolled in the Cardiovascular Health Study from 1989-1990.

Eating tuna or other broiled or baked fish at least once a week was associated with lower heart rate (-3.2 beats/minute) and a 50% lower likelihood of prolonged ventricular repolarisation (the period of time it takes the heart to recharge after it beats, so it can beat again), compared to those consuming fish less than once a month.

Eating fish at least 5 times per week was associated with an even healthier heart rhythm.

However, eating fried fish (typically sold in the U.S. as fish burgers or fish sticks) was not associated with increased blood levels of omega 3 fats or any beneficial electrocardiogram results.

In fact, a previous study led by the same researcher (Mozaffarian, Am J Cardiol 2006 Jan) found that while eating baked or broiled fish was linked to a slower but more powerful heart beat and lower blood pressure, eating fried fish was associated with heart muscle motion abnormalities, a reduced ejection fraction, lower cardiac output, and higher blood pressure.

Since irregular heart beats are a major precipitating factor in sudden death due to cardiac arrest, promoting a healthy heart rhythm by eating baked or broiled—not fried—fish several times a week makes very good sense. Happily, as our recipes, such Mediterranean Cod show, it's a quick, easy and most importantly, delicious prescription.

The INTERMAP is a study of lifestyle factors, including diet, and their effect on blood pressure in 4,680 men and women aged 40 to 59 living in Japan, China, the U.S. and the U.K. Blood pressure was measured and dietary recall questionnaires were completed by participants on four occasions. Dietary data was analyzed for levels of omega-3 fatty acids from food sources including fish, nuts, seeds and vegetable oils.

Average daily intake of omega-3 fatty acids was 2 grams. Participants with a high (o.67% kcal) omega-3 fatty acid percentage of their daily calorie intake had an average systolic and diastolic blood pressure reading that was 0.55/0.57 mm Hg less, respectively, than participants with lower intake. Previous research has found that a decrease of 2 mm Hg reduces the population-wide average stroke mortality rate by 6 percent and that of coronary heart disease by 4%.

Higher omega-3 fatty acid intake among the 2,238 subjects who were not using drugs, supplements, or a special diet for hypertension, heart disease, or diabetes was associated with a 1.01/0.98 mm Hg reduction in systolic and diastolic blood pressure, respectively.

For the 2,038 subjects in this group who did not have hypertension, greater intake was associated with a 0.91/0.92 mm Hg average systolic and diastolic reduction.

Lead author Hirotsugu Ueshima, MD of Shiga University of Medical Science in Japan, noted that the beneficial effect of omega-3 fats was even greater in people who had not yet developed high blood pressure.

The researchers also found that omega-3s from nuts, seeds, and vegetable oils—such as walnuts and flaxseed—had just as much impact on blood pressure as omega-3s from fish.
"With blood pressure, every millimeter counts. The effect of each nutrient is apparently small but independent, so together they can add up to a substantial impact on blood pressure. If you can reduce blood pressure a few millimeters from eating less salt, losing a few pounds, avoiding heavy drinking, eating more vegetables, whole grains and fruits (for their fiber, minerals, vegetable protein and other nutrients) and getting more omega-3 fatty acids, then you've made a big difference," said Ueshima.

Deep vein thrombosis is a dangerous condition in which blood clots develop in the deep veins of the legs, thighs or pelvis, causing swelling and pain. An embolism is created if a part or all of the blood clot in the deep vein breaks off from the site where it was created and moves through the venous system. If the clot lodges in the lung, a very serious condition, pulmonary embolism, arises.

Fortunately, a healthy way of eating offers significant protection, as demonstrated by a prospective study over 12 years that involved almost 15,000 middle-aged adults. While those eating the most red and processed meat doubled their risk of deep vein thrombosis (DVT), those in the upper 3 quintiles of fruit and vegetable intake had a 41-53% lower risk of DVT. And those eating fish, such as cod, at least once each week were found to have a 30-45% lower DVT risk. (Steffen LM, Folsom AR, et al.,Circulation)

Practical Tip: For protection against deep vein thrombosis, increase your consumption of fruit and vegetables; eat fish at least once a week; and decrease consumption of red and processed meats.

Protection Against Cancer

Fish consumption is also correlated with a reduced incidence of colon cancer. The selenium and vitamin B12 found in cod have all been shown to reduce the risk of the development of colon cancer by protecting colon cells from the damage caused by toxic substances found in certain foods and cancer-causing chemicals produced by certain gut bacteria.

Omega-3-Rich Fish Protective against Colorectal Cancer

A diet rich in the omega-3 fats found in cold water fish, such as cod, greatly reduces risk of colorectal cancer, indicates a study comparing 1,455 subjects with colorectal cancer to 1,455 matched healthy controls.

Those whose diets provided the most omega-3s had a 37% reduction in colorectal cancer risk, compared to those whose diets provided the least. Colorectal cancer risk was 41% lower in those with the highest average intake of EPA, and 37% lower in those whose diets supplied the most DHA. (Theodoratou E, McNeill G, et al., Am J Epidemiol.)

Fishermen have, in epidemiological studies, been identified as having a lower risk of leukemia, multiple myeloma and non-Hodgkin lymphoma, an occupational benefit that researchers thought might be due to the fact that they eat more fish.

Now, a Canadian study published in the April 2004 issue of Cancer Epidemiology Biomarkers & Prevention suggests that persons whose diet includes more weekly servings of fresh fatty fish have a much lower risk of these three types of cancer. Data drawn from a survey of the fish eating habits of 6,800 Canadians indicates that those consuming the most fatty fish decreased their risk of leukemia by 28%, their risk of multiple myeloma by 36%, and their risk of non-Hodgkin lymphoma by 29%. Overall, frequent eaters of fatty fish reduced their risk for all forms of lymphomas by 30%.

Cod and Other Fatty Fish Highly Protective against Kidney Cancer

Consumption of fatty fish, such as cod, offers significant protection against renal cell carcinoma, the most common form of kidney cancer, suggests evidence presented in a 15.3-year epidemiological study involving 61,433 women who participated in the Swedish Mammography Cohort Study (Wolk A, Larsson SC, JAMA).

Renal cell carcinoma (RCC), the 10th most common form of cancer with a male:female ratio of 5:3, accounts for more than 80% per cent of all kidney cancers. Although an earlier review of prospective cohort studies (MacLean et al, JAMA) did not support the hypothesis that fish consumption is protective, the authors of the new JAMA study point out that virtually all the other studies on the subject, including MacLean's, did not take into account whether the fish consumed were fatty or lean fish.(Fatty fish contain 20 to 30 times more omega-3 (DHA and EPA) than lean fish, which provide 3-5 times more vitamin D.)

When this distinction was considered, the researchers found that those who consumed one or more serving of fatty fish each week had a 44% decreased risk of RCC compared with those who consumed no fatty fish.

Plus, those who reported long-term consumption between the beginning of the study and the 10-year follow-up had a dramatic 74% lower risk.

In contrast, no association was found between consumption of lean fish or other seafood and incidence of RCC.

Wolk notes,"Our results support the hypothesis that frequent consumption of fatty fish may lower the risk of RCC, possibly due to increased intake of fish oil rich in EPA and DHA, as well as vitamin D."

Protection against Alzheimer's and Age-related Cognitive Decline

Can eating fish high in the omega-3 fatty acids, DHA(docosahexaenoic acid) and EPA (eicosapentaenoic acid), help lessen the cognitive decline and Alzheimer's disease growing in our aging population? A number of studies indicate the answer to this question is a resounding "Yes."

In a paper published in the journal Neuron (Calon F, Lim GP, et al.), researchers at the University of California, Los Angeles School of Medicine reported that a diet rich in DHA reduced the impact of a gene linked to the development of Alzheimer's disease.

Using mice bred to have genetic mutations that cause lesions typical of Alzheimer's, the researchers found that those fed a diet containing omega-3-rich fish did not develop the expected memory loss or brain damage. In contrast, mice fed safflower oil, which is low in the omega-3 fats and high in the omega-6 fatty acids, showed signs of synaptic damage in their brains that closely resemble those of people with Alzheimer's.

A report from the Framingham Heart Study published in the Archives of Neurology showed that persons whose blood levels of DHA placed them in the top quartile of values had a significantly (47%) lower risk of developing all-cause dementia than did those in the bottom quartile. Plus, greater protection against cognitive decline was obtained from consuming 2.9 than 1.3 fish meals per week. (Schaefer EJ, Bongard V, et al.)

Three additional positive studies have been published in the American Journal of Clinical Nutrition:

In the Zutphen Elderly Study, which involved 210 men aged 70-89 years (van Gelder BM, Tijhuis M, et al.), a linear relation was found between the estimated intake of DHA and EPA and prevention of cognitive decline.

A DHA+EPA intake of approximately 380 mg per day seemed to prevent cognitive decline. This amount of DHA+EPA would be found in just 20 grams (just 2/3 of one ounce) of Chinook salmon or in 100 grams (about 3 ounces) of cod.

Eating just two to three meals of fish a week would supply approximately 380 mg EPA+DHA per day.

In the Minneapolis study (Beydoun MA, Kaufman JS et al.) of 2251 men and women, risk of cognitive decline increased as levels of omega-6 (arachidonic acid) increased in subjects' cholesterol and other blood lipids, but decreased as the concentration of omega-3 fat (linoleic acid) increased in their blood fats.

Among subjects with high blood pressure and high cholesterol, cognitive decline was clearly associated with lower blood levels of omega-3 fats (DHA+EPA).

Subjects eating an average of at least 10 grams of fish a day (1 ounce = 30 grams, so eating just 2.1 ounces of fish each week would supply an average of 10 grams daily) had significantly better mean test scores and a lower prevalence of poor cognitive performance than those whose intake averaged less than 10 grams/day.

The associations between total seafood intake and cognition were strongly dose-dependent with maximum benefit observed at an intake of approximately 75 grams/day (this would translate to 2.5 ounces of fish per day or approximately four 4-ounce servings of fish per week). Almost all cognitive functions were beneficially influenced by eating fish, particularly nonprocessed lean fish and fatty fish. (Nurk E, Drevon CA, et al., Am J Clin Nutr.)

In all of these studies, fish consumption and the resulting increase in blood levels of omega-3 fatty acids significantly lessened mental decline over time.

How? A number of mechanisms have been suggested in recent studies to explain fish's protective effects against cognitive decline and Alzheimer's:

EPA's anti-clotting and anti-inflammatory actions promote a healthy blood supply to the brain and lower inflammation.

Since EPA and arachidonic acid are metabolized by the same enzymes, an increase in levels of EPA helps lessen the production of the pro-inflammatory compounds derived from arachidonic acid. (Arachidonic acid is a precursor of proinflammatory cytokines eicosanoids that are thought to be associated with greater cognitive decline.)

Increasing consumption of DHA may correct the DHA deficiency in the cerebral cortex characteristically seen in patients with Alzheimer disease.

DHA is involved in the membrane of ion channels in the brain, making it easier for them to change shape and transmit electrical signals.

DHA is the source of an anti-inflammatory compound made in the brain called NPD1 that lessens amyloid-beta production in cytokine-stressed human brain cells.

DHA slows the accumulation of tau, a protein involved in the development of neurofibrillary tangles, and also decreases beta amyloid formation by reducing levels of presenilin, the enzyme that separates beta amyloid from its parent protein. (Neurofibrillary tangles and beta amyloid plaques are the two types of brain lesions seen in Alzheimer's disease.)

Frank LaFerla, co-author of research published in the Journal of Neuroscience showing that DHA helps prevent the formation of neurofibrillary tangles and decreases beta amyloid formation, commented: "We are greatly excited by these results, which show us that simple changes in diet can positively alter the way the brain works and lead to protection from Alzheimer's disease pathology."
Practical Tip: To keep your cognitive edge, cut back on sources of omega-6 fats, such as beef, and corn, palm, peanut, safflower and sunflower oils, and enjoy omega-3-rich cold water fish, such as cod, at least 3 times each week.

Omega-3 Fat, DHA, Destroys Alzheimer's Plaques

DHA boosts production of the protein LR11, which destroys the beta-amyloid plaques associated with Alzheimer's disease, shows brain cell research.

"Because reduced LR11 is known to increase beta-amyloid production and may be a significant genetic cause of late-onset Alzheimer's disease (LOAD), our results indicate that DHA increases in LR11 levels may play an important role in preventing LOAD," wrote the researchers in the Journal of Neuroscience.

"Genetic polymorphisms that reduce LR11 expression are associated with increased AD risk," explained the researchers. "However these polymorphisms account for only a fraction of cases with LR11 deficits, suggesting involvement of environmental factors."

The new research investigated if fish oil and DHA could boost LR11 levels, since having high levels of LR11 have been reported to prevent plaque formation, while low levels in patients are believed to be a factor in causing the disease.

Even low doses of DHA increased the levels of LR11 in rat brain cells. Dietary DHA increased LR11 levels in the brains of rats or older mice genetically engineered to develop Alzheimer's disease. The positive effects of DHA on LR11 levels and the protection against Alzheimer's was again seen human brain cells were used. (Ma QL, Teter B, et al. J Neurosci.)

As a result of these findings, the National Institutes of Health has begun a large-scale clinical trial with DHA in patients with well established Alzheimer's disease. Lead researcher, Greg Cole, associate director of UCLA's Alzheimer Disease Research Center, thinks it may be too late for DHA to benefit these patients, but that DHA is highly likely to benefit patients in the earliest stages of Alzheimer's. And, we would add, help prevent the development of the disease in the rest of us!

DHA is the most abundant essential fatty acid in the brain, is crucial for healthy brain development, and low levels have been linked to cognitive impairment. According to the national Alzheimer's Association, approximately 5.1 million Americans suffer from Alzheimer's disease, a number that is projected to increase to 11 to 16 million sufferers by 2050.

Practical Tip: Enjoying several weekly servings of fish high in DHA, such as cod, is a smart move.

Omega-3-Rich Diet Improves Mood, Reduces Depression

When researchers from Ohio State University evaluated blood samples taken from 43 older adults (average age 67), they found that study participants with high ratios of omega-6 to omega-3 not only had higher levels of various compounds involved in inflammation, but were more likely to suffer from depression.

Both depression and stress promote the production of pro-inflammatory cytokines. Researchers measured a number of these pro-inflammatory compounds including tumour necrosis factor-alpha (TNF-alpha), interleukin-6 (IL-6), and the IL-6 soluble receptor (sIL-6r). Symptoms of depression were assessed using the Center for Epidemiological Studies Depression Scale.

Levels of pro-inflammatory cytokines increased progressively as depressive symptoms increased. But when depressive symptoms were combined with high omega-6:omega-3 ratios, levels of proinflammatory cytokines skyrocketed by up to 40% more than normal—far beyond the 18% increase resulting from the presence depressive symptoms alone.

Chronic inflammation has already been linked to heart disease, type 2 diabetes, osteoporosis, cognitive decline and Alzheimer's. Earlier epidemiological (population) studies have also linked higher levels of pro-inflammatory cytokines with depressive symptoms. This new study suggests that a diet that is rich in omega-6 fats but includes few of the foods rich in omega-3 fats—such as the standard American diet—promotes not only inflammation, but depression.

The positive take-away is that increasing consumption of foods rich in omega-3s, while decreasing consumption of omega-6-rich foods, can provide some protection against depression, particularly as depressive symptoms increase.

Omega-3s are found in cold water fish, nuts, such as walnuts, and flaxseeds. Alpha-linolenic acid (ALA), the omega-3 in nuts and seeds, can be converted—albeit inefficiently—in the body to the omega-3s found in fish, eicosapentaenoic acid (EPA) and docosahexaenioc acid (DHA).

EPA improves blood flow and is also suggested to affect hormones and the immune system, both of which have a direct effect on brain function. DHA is active in the membrane of ion channels in the brain, making it easier for them to change shape and transmit electrical signals, and is involved in serotonin metabolism (reduced serotonin production and/or activity is a key factor in depression).
Practical Tip: Be of good cheer. Cut back on sources of omega-6 fats, such as beef, and corn, palm, peanut, safflower and sunflower oils. Enjoy a handful of omega-3-rich walnuts and/or flaxseeds daily, and a serving of cold water fish, such as cod, at least 3 times each week.

Reduce Your Risk of Macular Degeneration

A diet high in omega-3 essential fatty acids, especially from fish, offers significant protection against both early and late age-related macular degeneration (AMD), show two studies published in the July 2006 issue of the Archives of Opthalmology.

In age-related macular degeneration, the area at the back of the retina called the macula, which controls fine vision, deteriorates, resulting in central vision loss and even blindness. AMD is the leading cause of blindness in people over 50, affecting more than 30 million people worldwide.

In the first study, Brian Chua and colleagues in Sydney, Australia, utilized data from the Blue Mountains Eye Study, which enrolled 3,654 men and women aged 49 and older between 1992 and 1994. Dietary questionnaires completed by 2,895 participants at the beginning of the study provided information on fatty acid intake.

Participants among the top one-fifth in terms of omega-3-rich fish consumption had a 42% lower risk of early AMD compared to those whose fish intake placed them in the lowest fifth. Enjoying omega-3-rich fish at least once a week provided a a 42% reduction in risk for early AMD.

Eating omega-3-rich fish at least three times a week was associated with a 75% reduction in late AMD.

In the second study, Johanna M. Seddon and colleagues at the Massachusetts Eye and Ear Infirmary, Harvard Medical School, Boston, looked at modifiable and protective factors for AMD among elderly male twins enrolled in the National Academy of Sciences—National Research Council World War II Veteran Twin Registry. Of the 681 twins examined, 222 were found to have intermediate or late stage AMD, and 459 twins had no signs of AMD.

Current smokers had a 1.9-fold (almost double) increased risk of AMD. Even past smokers' risk was highly elevated—a 1.7 increase compared to men who never smoked.

Eating more fish, however, greatly reduced AMD risk. Among the men whose fish consumption put them among the top 25% of dietary omega-3 fatty acid intake, risk of AMD was 45% lower compared to those with the lowest fish / omega-3 intake.

Eating fish at least twice a week reduced AMD risk by 36% compared to those who ate less than one serving of fish per week.
The authors noted that AMD is highly preventable simply by following a healthy lifestyle: "About a third of the risk of AMD in this twin study cohort could be attributable to cigarette smoking, and about a fifth of the cases were estimated as preventable with higher fish and omega-3 fatty acid dietary intake."

Anti-Inflammatory Nutrients Reduce Asthma, Arthritis and Migraine

The selenium and omega-3 fats concentrated in cod have anti-inflammatory actions that reduce the inflammation that can lead to asthma attacks, rheumatoid arthritis and osteoarthritis, and even migraines. Studies have shown that children who eat fish several times a week are at a much lower risk of developing asthma than children who don't eat fish. The selenium in cod helps prevent asthma attacks by regenerating antioxidants that are used to reduce the free radical damage that can lead to severe attacks. Selenium is indirectly responsible for keeping the body's supply of at least three vitally important antioxidants intact: these are vitamin C, glutathione, and vitamin E. Although the chemistry of these relationships is complicated, it centers around an enzyme (protein molecule in the body that helps "jump start" a chemical reaction) called glutathione peroxidase. This enzyme cannot function without selenium.

The essential fatty acids found in cod have also been shown to prevent the progression of osteoarthritis and rheumatoid arthritis. In fact, in societies where fish is eaten regularly, the rate of rheumatoid arthritis is much lower than in areas where fish is not commonly eaten.The anti-inflammatory actions of the omega-3 fats found in cod reduce the inflammation that is central to the symptoms and progression of rheumatiod and osteoarthritis, and may also help prevent migraine attacks, which are triggered by an inflammatory cascade that spreads from neuron to neuron in the brain called spreading depression. A four-ounce serving of cod provides 13% of the daily value for these beneficial omega-3 fats.

Fish and Whole Grains Highly Protective against Childhood Asthma

According to the American Lung Association, almost 20 million Americans suffer from asthma, which is reported to be responsible for over 14 million lost school days in children, and an annual economic cost of more than $16.1 billion.

Increasing consumption of whole grains and fish could reduce the risk of childhood asthma by about 50%, suggests the International Study on Allergy and Asthma in Childhood (Tabak C, Wijga AH, Thorax).

The researchers, from the Dutch National Institute of Public Health and the Environment, Utrecht University, University Medical Center Groningen, used food frequency questionnaires completed by the parents of 598 Dutch children aged 8-13 years. They assessed the children's consumption of a range of foods including fish, fruits, vegetables, dairy and whole grain products. Data on asthma and wheezing were also assessed using medical tests as well as questionnaires.

While no association between asthma and intake of fruits, vegetables, and dairy products was found (a result at odds with other studies that have supported a link between antioxidant intake, particularly vitamins C and E, and asthma), the children's intake of both whole grains and fish was significantly linked to incidence of wheezing and current asthma.

In children with a low intake of fish and whole grains, the prevalence of wheezing was almost 20%, but was only 4.2% in children with a high intake of both foods. Low intake of fish and whole grains also correlated with a much higher incidence of current asthma (16.7%). compared to only a 2.8% incidence of current asthma among children with a high intake of both foods.

After adjusting results for possible confounding factors, such as the educational level of the mother, and total energy intake, high intakes of whole grains and fish were found to be associated with a 54 and 66% reduction in the probability of being asthmatic, respectively.

The probability of having asthma with bronchial hyperresponsiveness (BHR), defined as having an increased sensitivity to factors that cause narrowing of the airways, was reduced by 72 and 88% when children had a high-intake of whole grains and fish, respectively.
Lead researcher, CoraTabak commented, "The rise in the prevalence of asthma in western societies may be related to changed dietary habits." We agree. The Standard American Diet is sorely deficient in the numerous anti-inflammatory compounds found in fish and whole grains, notably, the omega-3 fats supplied by cold water fish and the magnesium and vitamin E provided by whole grains. One caution: wheat may need to be avoided as it is a common food allergen associated with asthma.

Protection against Sunburn

Another benefit of omega-3s anti-inflammatory effects may be their ability to protect our skin against sunburn, and possibly, skin cancer.

Although our increased susceptibility to skin cancer is usually blamed on damage to the ozone layer, dietary changes over the last 75 years, which have resulted in excessive consumption of omega-6 fatty acids and insufficient consumption of omega-3 fats, may also be causing human skin to be more vulnerable to damage from sunlight.

Research by Dr Lesley Rhodes, Director of the Photobiology Unit at the University of Manchester, UK, suggests that eating more omega-3-rich fish, such as cod, could lessen the inflammation induced by UV-B radiation and help prevent not only the damaging effects of sunburn, but possibly skin cancer as well.

In a paper published in January 2005 in the Journal of Investigative Dermatology, Rhodes explored the ability of omega-3s to protect epidermal and dermal skin cells against UV-B-induced triggering of tumor necrosis factor-alpha, a molecule that induces the production of the pro-inflammatory cytokine, IL-8. Both EPA and DHA significantly suppressed TNF-alpha-induced IL-8 secretion—by 54% in the case of EPA and 42% by DHA.
In an earlier one of Dr Rhodes studies, published in the May 2003 issue of Carcinogenesis, 42 healthy volunteers were given a measured dose of ultraviolet light, then divided into two groups. One group was given a daily 4 gram omega-3 fish oil supplement, while the other group received olive oil. After three months, when their responses to ultraviolet light were again measured, the skin cells of volunteers receiving fish oil experienced significantly less DNA damage, leading Rhodes to suggest that increasing consumption of omega-3-rich fish might reduce skin cancer in humans.

Description

It's not surprising that the words "cod" and "cold" are so similar, just differing by one letter. It's not surprising since cod need the cold. They need to live in deep, artic temperature water to grow, reproduce and survive.

Although there are a few varieties of cod that are generally consumed, North Atlantic cod (Gadus morhua) is the most reputed and well known type. It has a light color and a noble taste. Other types of cod that are eaten throughout the world include ling cod, saithe cod and zarbo cod.

Cod belong to the same family (Gadidae) as both haddock and monkfish.

History

People have been enjoying cod as a food ever since this beautiful fish appeared in the Earth's waters, basically since time immemorial.

Like other fish, in addition to being consumed fresh, preservation techniques such as salting, smoking and drying were used to preserve the cod. This allowed it to be easily transported and stored and made it one of the most commercially important fishes during the Middle Ages in Europe. Salted and dried cod is still very popular today in many countries including Norway, Portugal and Brazil.

Ever wonder where Cape Cod, Massachusetts, got its name? The answer: from this fish that used to be abundant in the coastal waters of this seaside town as well as the eastern seaboard of the United States and Canada. Unfortunately, over-fishing during the past few decades has greatly diminished the amount of cod in these waters. In addition to North America, much of the cod available in today's market comes from Norway, Greenland, and Iceland.

How to Select and Store

Just as with any seafood, it is best to purchase cod from a store that has a good reputation for having a fresh supply of fish. Get to know a fishmonger (person who sells the fish) at the store, so you can have a trusted source from whom you can purchase your fish.

Fresh whole cod should be displayed buried in ice, while fillets should be placed on top of the ice. The flesh of the cod fillets should gleam and have minimal gaping.

Smell is a good indicator of freshness. Since a slightly "off" smell cannot be detected through plastic, if you have the option, purchase displayed fish as opposed to pieces that are prepackaged. Once the fishmonger wraps and hands you the fish that you have selected, smell it through the paper wrapping and return it if it does not smell right.

When storing all types of seafood, including cod, it is important to keep it cold since fish is very sensitive to temperature. Therefore, after purchasing cod or other fish make sure to return it to a refrigerator as soon as possible. If the fish is going to accompany you during a day full of errands, keep a cooler in the car where you can place the cod to make sure it stays cold and does not spoil.

The temperature of most refrigerators is slightly warmer than ideal for storing fish. Therefore, to ensure maximum freshness and quality, it is important to use special storage methods to create the optimal temperature for holding the fish. One of the easiest ways to do this is to place cod, which has been well wrapped, in a baking dish filled with ice. The baking dish and fish should then be placed on the bottom shelf of the refrigerator, which is its coolest area. Replenish ice one or two times per day.

The length of time that cod can stay fresh stored this way depends upon how fresh it is, i.e. when it was caught. Fish that was caught the day before you purchased it can be stored for about four days, while fish that was caught the week before can only be stored for about one or two days.

How to Enjoy

A Few Quick Serving Ideas

Combine cod, broth, healthy sautéed onions and garlic, and your favorite vegetables and seasonings in a stock pot to make a delicious fish soup.

Safety

Cod and Food Allergies

Fish, such as cod, are among the eight food types considered to be major food allergens in the U.S., requiring identification on food labels. For helpful information about this topic, please see our article, An Overview of Adverse Food Reactions.

Introduction to Food Rating System Chart

The following chart shows the nutrients for which this food is either an excellent, very good or good source. Next to the nutrient name you will find the following information: the amount of the nutrient that is included in the noted serving of this food; the %Daily Value (DV) that that amount represents (similar to other information presented in the website, this DV is calculated for 25-50 year old healthy woman); the nutrient density rating; and, the food's World's Healthiest Foods Rating. Underneath the chart is a table that summarizes how the ratings were devised. Read detailed information on our Food and Recipe Rating System.